During the past several years, substantial improvements have been made in three dimensional (3D) seismic surveys to better locate and define the boundaries of underground hydrocarbon producing formations. During this same time period, substantial improvements have also been made in directional drilling and horizontal well completion techniques. As a result, many current well completions often include more than one wellbore or borehole. For example, a generally vertical wellbore may be initially drilled adjacent to one or more hydrocarbon producing formations. Multiple wellbores may then be drilled from the vertical wellbore to optimize production from the adjacent hydrocarbon producing formation or formations. Such well completions are often referred to as multilateral wells.
A typical multilateral well completion will include a generally vertical or primary wellbore defined in part by a casing string and a layer of cement disposed between the exterior of the casing string and the inside diameter of the primary wellbore. Directional drilling equipment and techniques may be used to form an exit or window in the casing string and layer of cement at a downhole location selected for drilling a lateral or secondary wellbore from the primary wellbore. Directional drilling equipment and techniques may also be used to drill the lateral or secondary wellbore from the primary wellbore.
The location of the exit or window from the primary wellbore, the orientation of the window, the length of the secondary wellbore and the orientation of the secondary wellbore relative to the primary wellbore are selected based on the characteristics of the associated hydrocarbon producing formation. For many locations such as deep offshore wells, multiple lateral wellbores will be drilled from each vertical wellbore in an effort to optimize hydrocarbon production while minimizing drilling costs. Selective isolation and/or reentry into each of the secondary wellbores is often necessary to further optimize production from the associated hydrocarbon producing formations.
The process of drilling and using lateral wellbores, however, suffers several disadvantages. For example, equipment such as drilling and logging devices must transition to and from the lateral wellbore without becoming lodged at an intersection of the primary wellbore and the lateral wellbore. For instance, one example of a logging tool used to analyze material surrounding a wellbore includes four arms with springs, called bow spring centralizers. The bow spring centralizers expand within the wellbore to centralize the logging tool within a wellbore. During insertion or retrieval of the logging tool, however, the bow spring centralizers may become lodged or broken at the intersection of the primary wellbore and the lateral wellbore.